Serb forces are torching houses in Kosovo in an attempt to thwart ethnic Albanian guerrillas, threatening a new flood of refugees fleeing homes in the southern Serb province.

In recent weeks smoke has increasingly been seen pouring from a cluster of villages near the western town of Klina and north of the regional capital, Pristina, as Serb forces try to clear villages of Kosovo Liberation Army (KLA) guerrillas.

The burnings, which come amid last-chance peace talks in Paris, were confirmed by a senior Western official who visited the village of Ivaje, near the Macedonian border earlier this month. He estimated that the Serbs had burned about 20 per cent of homes there.

The Guardian saw two houses burned in the nearby village of Pustenik. And fires burned when Serb forces moved against the KLA to the north of Pristina last week.

Houses torched near the Macedonian border were probably buildings commandeered by the KLA, said the Western official. But he said the blazes around Vucitrn, particularly in the village of Mijalic on Monday night, followed a pattern of indiscriminate arson seen in an offensive last year which aimed to crush the KLA's widespread support.

'Around Vucitrn, we felt there was less discrimination. There are certainly allegations of less disciplined behaviour,' the official said.

Thousands of ethnic Albanian civilians have been displaced, some forced to flee their homes for the second or third time.

Serb tanks and armour massed at three points around the village of Svrka, near Kosovo's western town of Klina, at the weekend. Most of the civilians had already fled when the Yugoslav army started lobbing mortar rounds into the village to try to force out guerrillas.

'I was very afraid to come here today,' said 52-year-old Shefkie Berisha who with her son, aged 13, returned to inspect the ruin of her Svrka home on Monday. She had taken her five children south a few days earlier. 'They [Serb forces] are doing the same as they did last year,' she said.

A further sign of gathering war clouds came with Monday's announcement by the Yugoslav state news agency, Tanjug, that military service has been extended because of the Nato air strike threat levelled at Yugoslavia if it fails to sign up to the West's interim autonomy deal for Kosovo.The Western official said the Yugoslav army already had five times the forces permitted in Kosovo under a now ragged peace deal clinched last October.

The Belgrade newsletter VIP warned this week that the Yugoslav president, Slobodan Milosevic, could be about to 'launch a fierce crackdown on the KLA, probably with a large number of civilian casualties, before the arrival of Nato'.

The Western official said that KLA numbers had increased since the massacre of ethnic Albanians at the village of Recak in January, and added that there were signs that the guerrillas were making more effective use of the RPG-7, a rocket-propelled grenade.

 A car bomb in Sarajevo critically injured an ethnic Croat official of the Muslim-Croat federal government yesterday.

Jozo Leutar, the federation's deputy interior minister who is known to be tough on organised crime, underwent surgery to remove a piece of metal which had become lodged in his brain.

James Fergusson, a spokesman for Bosnia's top international official, Carlos Westendorp, said: '[Westendorp] is aware of Mr Leutar's strong stance in the fight against corruption in Bosnia-Herzegovina and wishes to pay tribute to his courage and leadership in that struggle.'